Remove API_AVAILABLE(ios(10.0)) / API_AVAILABLE(ios(12.0)) (#35835)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/35835

The minimum iOS version for react-native-macOS is 12.4 at this time.
These checks can be removed.
See: https://github.com/microsoft/react-native-macos/issues/1605

Changelog: [Internal]

Reviewed By: cipolleschi

Differential Revision: D42523417

fbshipit-source-id: 45e7c0b6f31710dd6fcace0eb624e52489599e09